An antenna is that part of a transmitting or receiving system which is designed to radiate or to receive electromagnetic radio waves. Optimal performance for radio systems such as cellular and cordless radiotelephones is obtained when a antenna protrudes into free space away from a housing which encloses the radio system. For such radiotelephones the antenna is typically at least as long as the housing containing the radiotelephone. The portability of a radiotelephone is comprised when permanently affixed in its protruding position outside the radiotelephone's housing. To improve the portability of radiotelephone when its not in use, mechanisms have been devised which enable the operator to easily disconnect the antenna or to conceal the antenna within the radiotelephone's housing. The mechanisms usually require the radiotelephone operator to manually alter the position of the antenna with respect to the radiotelephone. Additionally, damaged antennas which are concealed within the radiotelephones housing usually cannot be replaced by the operator without opening the radiotelephone's housing.
A conventional mechanism for coupling an antenna to a radiotelephone is used on a Motorola portable cellular radiotelephone model number 980XL. The mechanism, a standard BNC radio frequency connector, enables the operator to easily disconnect a fixed helical antenna for increased portability or connect the antenna to use the radiotelephone.
A similar mechanism is used on a cordless radiotelephone manufactured by Sanyo (model number CLT8801). The mechanism uses a conventional threaded radio frequency connector to connect or disconnect a fixed helical antenna. The conventional mechanism used with the Sony cordless radiotelephone and the aforementioned Motorola cellular radiotelephone require manual coupling and decoupling of the antenna to the radiotelephone. This presents an operating inconvenience to the operator and the potential for the operator to lose the antenna when it is detached. An advantage of these coupling mechanisms, however, is that the operator can easily replace a damaged antenna without opening the radiotelephone's housing.
A mechanism which enables an antenna to be concealed within the radiotelephone's housing is used on a cordless telephone manufactured by AT&T (model number 4600). The mechanism uses a conventional telescoping metal antenna. To use the radiotelephone, the operator manually extends the telescoping antenna. When the radiotelephone is not in use, the operator manually retracts the telescoping antenna. If the antenna is damaged, the operator can replace the telescoping mechanism by accessing a conventional threaded connector on the outside of the radiotelephone's housing. Although the telescoping antenna mechanism is operator replaceable and concealed within the radiotelephone when not in use, manual extension and retraction of the antenna is inconvenient for the operator.
A second mechanism which enables an antenna to be concealed within a radiotelephone housing is used on a cordless radiotelephone manufactured by Panasonic (model number KX-T3725). The operator is required to manually extend or retract a fixed helical antenna. The electrical connection between the fixed helical antenna and the radiotelephone is aided by an extension coiled antenna. Although this antenna mechanism allows the convenience of concealing the antenna within the radiotelephones housing, the antenna is not operator replaceable without opening the radiotelephone's housing and the manual positioning of the antenna is an operator inconvenience.
A third mechanism enabling an antenna to be concealed within a cordless radiotelephone is also manufactured by Panasonic (model number KX-T4000). To extend the antenna the operator is required to release a latch enabling the antenna to actively project away from the radiotelephone's housing. The semiautomatic extension of the antenna is a hazard for a device which is normally used in close proximity with an operator's eyes. Although the antenna can be conveniently concealed within the cordless radiotelephone's housing, the antenna cannot be replaced by the operator without opening the radiotelephone's housing.
A formidable challenge, therefore, is to develop an antenna for portable radio systems which can be concealed within the radio system's housing, is operator replaceable without opening the radiotelephone's housing and can be semiautomatically retracted inside the radiotelephone's housing for operator convenience.